There is often a need to identify blood vessels and assess blood flow status in identified vessels during minimally invasive medical procedures. In gastroenterologic endoscopy, examples of such instances include the identification of vessels in peptic ulcer bases, which guides subsequent management of these lesions, identification of vessels at risk prior to polypectomy, and identification of aberrant vessels at risk for bleeding prior to sphincterotomy. Other specialties would yield additional examples of such minimally invasive techniques and procedures.
Currently, vessels in peptic ulcer bases are only identified visually; these subjective observations are then used to grade ulcers via endoscopic stigmata of recent hemorrhage (ESRH) or similarly, the Forrest classification system. According to the Forrest Classification system, lesions are classified according to their appearance from a Class Ia to a Class III. The classes are as follows: Ia—spurting arterial hemorrhage, Ib—oozing hemorrhage, IIa—visible vessel, IIb—adherent clot, IIc—pigmented spot, III—no signs of recent hemorrhage. The use of ESRH or the Forrest classification system have been shown to be fraught with interobserver variability and the need for an objective method of grading peptic ulcer lesions to assess bleeding risk has been voiced by many in the GI field.
Furthermore, there is a need to assess the adequacy of endoscopic treatment of peptic ulcers. Currently, the GI endoscopist has no way of ascertaining whether an injection or coagulation therapy applied to an ulcer base has adequately occluded or obliterated the vessel at risk for recurrent bleeding. Despite advances in the endoscopic treatment of peptic ulcers, the rebleeding rate of lesions treated endoscopically remains high (quoted in the literature from less than 10% for combination therapies but as high as 30% for single therapies).
In addition, subsurface vessels are not readily visualized during laparoscopic procedures. Tactile sensation, which aids surgeons in the identification and evaluation of vessels in open surgical procedures, is not often available to the surgeon during laparoscopic surgery. In urologic surgery, the advancement of minimally invasive techniques has recently allowed for a laparoscopic approach to technically challenging procedures, which were previously only undertaken in an open fashion. Thus, there is an increasing need to identify blood vessels during laparoscopic urologic surgery
Currently, subsurface vessels are identified by the use of anatomical landmarks and meticulous dissection techniques during laparoscopic urologic procedures. Meticulous dissection to identify a vessel, while necessary to avoid inadvertent injury to the vessel, adds significant time to the surgical procedure. In addition, vessels may be present in an “aberrant” anatomical pattern, making the use of landmarks deceiving. This is of increased significance during laparoscopic nephrectomy, during which several vessels have to be identified and control gained. Additionally, vessels can present aberrantly in 25-40% of kidneys. Finally, abundant fatty tissue surrounding the kidneys adds an additional layer of complication to the identification of the renal vasculature during laparoscopic nephrectomy.
Other indications in which the localization of the vasculature has become increasingly important include laparoscopic partial nephrectomy and laparoscopic nerve sparing radical prostatectomy. In partial nephrectomy, it is critical to identify the feeder artery to the tumor being excised while in radical prostatectomy, identification of the neurovascular bundle facilitates sparing of the cavernous nerves.
Other fields employing minimally invasive techniques such as arthroscopy, bronchoscopy, laryngoscopy, mediatinoscopy, thoracoscopy, cystoscopy, ureteroscopy, hysteroscopy, neuroendoscopy, robotic-assisted surgical procedures, and surgical fields in which laparoscopic surgery is utilized, present a similar inability to palpate tissue surfaces to assess blood flow. What is needed, therefore, are techniques and apparati for assessing blood flow during minimally invasive medical procedures.